I can tell you from personal experience of alpine climbing and military ops/exercises that the Jetboil has never let me down. If you are concerned about stability, yes, there is the stabiliser that clips to the gas cartridge base but I would also suggest the hanging kit. It allows the whole unit to hang from a branch, bolt, ceiling, tent pole, whatever, and you don't have to worry about spilling stuff. It may not be as good a design as the Primus or anything else but it does work and it has history on its side: it's been around a few years and any problems have been resolved.
I haven't used the Primus ETA, or the new MSR super-efficient stove, so I can't compare them but all I can say is that the Jetboil has been a lifesaver (in the true sense of the word). It is so simple and gets your water boiling quickly and easily in situations where you do NOT want to be fannying around with fire-sticks, pressure stoves, bow-drills, flint/steel, tinder, wood, etc. I'm all for learning and using new skills but when my life is on the line, I ensure that I have something quick and reliable to hand. You don't get wood/tinder and natural cordage on the upper slopes of 4000m peaks.